[bug-mailutils] how to make mail.mailutils invoke sendmail without -f

[Forest]

Hi there.

I'm trying to solve a problem caused by mail.mailutils invoking sendmail
with the -f option.  (This option overrides my MTA's smart-host MAIL FROM
setting, leading to rejected outgoing messages.)  I'm looking for a way to
tell mailutils not to use the sendmail -f option.

I spent half the day trying to decipher the mailutils docs and experimenting
with /etc/mailutils.conf settings.  For example:

  mailer {
  url "prog://sendmail?-oi&$rcpt";
  };

I verified that my conf file is being used, but mailutils 3.4 (from the
ubuntu repositories) seems to ignore that particular setting.

Can someone help me, please?